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Damage to structures during venting and their removal
Vent introduction can cause major damage to cardiac structures. This injury can be either local or distant. The cannulation site may tear and this tear can extend in to adjacent structures. An aortic root vent can cause a dissection.If the dissection is local and superficial, incising and externalizing the dissection can prevent further dissection and a precise closure of the hole needs to be done.If it is large enough to prevent direct closure a piece of prosthetic patch or Glutaraldehyde treated pericardium may be used to patch the defct. this If there is a major dissection, the aorta needs to be opened and the dissection flap closed and the necessary amount of aorta needs to be either glued or resected and replaced with a prosthetic graft. Posterior wall injury can occur if the vent needle hits the posterior wall. This can be avoided by placing this needle (which doubles as a cardioplegia needle) prior to initiation of CPB r when placed on CPB the adjacent tissue is picked up and stabilized with a forceps to prevent the needle hitting the posterior wall. Bleeding posteriorly may usually be managed by placing a few strategically placed sutures on the tear site after lowering the aortic pressure either with sodium nitroprusside or restitution of CPB. If this fails, the aorta needs to be cross clamped, an aortotomy done and transluminal suturing of the defect need to be done. If the hole is large and precludes direct suture, trimming of the edges and placing a prosthetic /pericardial patch may be required. There can be bronchial injury due to forceful insertion of an RSPV vent. This may require the RSPV to be opened into the LA and the length of the vein to allow transluminal correction of the bronchial defect after opening the posterior wall of the RSPV. Some thymic fat may be interposed in between the bronchus and the posterior wall of the RSPV to prevent a broncho-atrial fistula. Patching of the RSPV may be required in case it gets narrow on closure.. The original purse string for placing the RSPV must take into account the curvature of the RSPV and its entry into the LA. Failure to take the purse string such that the "flexion crease" is not included in the purse string can cause a channel under the purse string that can cause persistent bleeding under the tightened purse string. The RSPV vent can be directed through the LA and via the mitral valve into the LV. Excessive suction can cause herniation of LV muscle into the holes of the vent and can cause LV apical rupture. This may require initiation of CPB, pledgetted sutures or amputation of the apex. At times the damage may not allow sutures so a large patch may have to be glued to the apex using bioglue as a life saving measure. An LV Apical vent should always be placed in a fat free area. Failure to do so can cause troublesome hemorrhage that can be very difficult to control post operatively. If the vent is placed too cranially it can injure the base of the anterior papillary muscle. It is better to close the LV Apex with an initial U stitch followed by a second over and over stitch. This has to be done preferably when the heart is contracting on full bypass. This allows the suture to be tightened with just enough force. Closure on a flaccid heart can sometimes lead to sutures cutting through when the heart starts contracting. The pulmonary artery vent site can extend and the tear needs to be precisely sutured. All PA vent sites should be secured with a double purse string as they can cut through. Beware of placing a PA Vent in a hypertensive PA it may be difficult to control. The PA vent must always be introduced in at least a partially full state as the pulmonary artery may be perforated posteriorly. This may require restitution of bypass and opening the PA and suturing the posterior rent through the PA. Bites taken here must be careful especially if the tear extends proximally as the left main and the pulmonary valve cusps may be at danger by careless deep bites.